The present invention relates generally to a circuit for improving the rise time of an electronic signal, and more particularly to an assist circuit for improving the rise time of signals on conductors of an open-drain NMOS data transfer bus in a data processing system.
Data processing systems contain data transferred buses such as, for instance, a data bus between a processor and a memory. Assist circuits are known which, at or near the beginning of the processor to memory cycle, supply current to each conductor in the data bus to quickly set each conductor in the data bus to its inactive state. By use of such assist circuits, the processor does not need to supply all of the current to return the conductors in the data bus to their inactive states, but needs only to change selected conductors in the data bus to their active states which correspond to data to be transferred. In prior known bus assist circuits, the supply of current to the data bus conductors is controlled by a clock circuit which also controls the processor to memory cycle.